Process for purifying continuously-circulating machinery-lubricating oils



Feb. 7, 1928. 1,658,362

R. G. WALKER PROCESS FOR PURIFYING CONTINUOUSLY GIRGULATING MACHINERYLUBRICATING OILS Filed FBli)o 4, 1926 Patented F ch". 7, 1928.

UNITED STATES PATENT. OFFICE.

ROBERT G. WALKER, OF NEW YORK, N. Y., ASBIGNOIB TO DE LAVAL SEPABATOBCOMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

rnocass ron roan-arms courInuousLY-cmcmrme IAGHInEBY-LUBBIGATIIG one.

Application filed February 4, 1926. Serial No. 86,867.

In. certain machinery, as, for example, rollin mills and engines ormotors for driving t e same, it is necessary to pump oil, 'in an endlesscircuit, insubstantial volume and at a substantial velocit through thebearings of the machinery. n rollin mills, due to the heavy workperformed y the rolls, the engine drive must be a direct one and theengine must be located in close proximity to the mills. Under theconditions existing in such a mill, the oil from the engine bearings, aswell as the oil from the roll bearings and gears, becomes speedily andseriously contaminated, not only metal and other materials of highspecific gravity. Due to the great volume of oil that, in a given time,flows through the bearings, it is deemed impracticable to economicallypurify it in circuit. 'There is, of course, no timefor gravityseparation, while centrifugal separation would require an impracticablylarge number of centrifuges; and, moreover, a centrifuge is not adaptedto remove certain of the heavier bulkier impurities which the oil picksup.

I have, however, developed a process for purifying the oil in circuitwhich is both eificient and economical. In my process, the more readily,precipitable contaminating materials, and especially those materials ofhigh specific avity and considerable bulk which a centrifuge is leastwell adapted to remove, are preferably removed by gravity settlement assoon, as possible after the oil leaves the bearin and before itssubjection to further puri cation treatment. I have found that a minordegree of contamination does not militate against the effectiveness ofthe oil for lubricaing purposes, but that the impairment of lubricatingefiiciency is due tocumulative contamination arisin from repeated travelof the oil through is e circult. I take the oil, as it comes from thebearings, and preferably after it is to a minor degree purified bygravity settlement, and by-pass apart of the 'oil through one or morecentrifuges and mix the centrifugally purified oil with the oil in themain ings. Thereby the degree of contamination of the oil is muchreduced and it is put into' with dirt, dust .and' scale but also withstream that is conducted back to the bearwould be for the degree ofcontamination to increase with repeated circulation of the oil, althoughthe oil would be efiicient for lubricat ng purposes for a much longertime than with no revisions for purification. My process is a apted,however, to maintain the Oil in a condition of substantial purity, andhence of lubricating efliciency, for an indefinite time, or at least aslong as the mill may be maintained in continuous operation. Toaccomplish this result, I convey the oil from the bearings to a tankwherein the preliminary artial gravity purificat on occurs. From t istank, the 011 1s adapted to overflow into a second tank. Only the mostreadily precipitable contaminat-lng materialswill settle in this tank,because the oil is constantly being admltted thereto and is constantlyoverflowing therefrom, so that, unless the tank be made of impracticablylarge dimensions, there is cons1derable surging in the tank. This lackof quiescenceis unfavorable to thorough gravity separation, even if suchmode of separat on would be eifective to remove all the constituents ofhigher specific gravity than the oil. Asheretofore stated, however,certa n contaminating materials will settle therem, and among suchmaterials are those the capacity to remove which by a centrifuge 1s moreor less uncertain.

The oil that overflows into the second tank is skimmed from the top ofthe first tank so that there is no danger of the passage into the secondtank of the most read- 11y precipitable materials. In the second tank,the conditions of surgin or lack of quiescence, is present as in thefirst tank and due to this condition, and to the comparatlvely shorttime during which the oil is present in the tank, the tendency togravity separation 1s not particularly strong. It is, however,- veryappreciable, and consequently, the oil to be centrifugally urified istaken preferably, from near the ottom, or from a lower zone, of thetank, so that there passes to the centrifuge the most heavilycontaminated part of the oil that has passed into the second tank.

From the second tank, that oil that is not by-passed to the centrifugeoverflows into a third tank. Theoil flowing direct from the second tankto the third tank, being skimmed from the top of the second tank,

is comparatively, although by no means absolutely, pure; butapproximates, although it does not reach, the degree of purity requiredfor re-use in the bearin The oil that is by-passed to the centri ugeshould be heated before admission to the centrifuge, as heating reducesthe viscosity of the oil, thus facilitating the separation ofcontaminating constituents.

The oil from the centrifuge is passed to the third tank, where it ismixed with the less pure oil that has overfiowed thereinto, therebyproviding a mixed oil having the degree of purity required forlubrication.

By this process, the tendency of the oil to slowly become more and morecontaminated by reason of only a fractional centrifugal purificationthereof is nearly or quite counteracted; that is, centrifu a1purification is constantly supplemented y some degree of gravitypurification, while the fraction of the 011 that, in any circuit of theoil, is subjected to centrifugal purification is the fraction thatcontains the largest percentage of impurities, so that the tendency tocumulative degeneration of the oil is almost completely neutralized.

The drawing is an elevational diagrammatic view of one form ofpurification plant adapted to carry out my process.

From the bearings of a rolling mill, rolling mill engine, or othermachine, the oil is drained into a tank a. In this tank an initial andvery partial settlement occurs, the constituents removed being largelythose which a centrifuge is least well adapted to remove. Tank 01 shouldbe provided with a drain a, normally closed, through which sediment maybe withdrawn while themachinery is out of operation. From tank a, theoil overflows into a tank I). From this tank the oil is removed at thesame rate at which it is supplied to the tank. A part of the oil ispumped, through a pipe line (7, to a heaterf, and thence to one or morecentrifugal purifiers 9. From these purifiers the purified oil flows,through a pipe" line it,

to a third tank 0, which receives the overflow from tank b. if the oilshould be pumped to the centrifuges as fast as it is admitted to tankI), there would be no overflow into tank 0; but the handling of all theoil by centrifuges being impracticable and uneconomical, there isnormally considerable overfiow into tank a. The oil pumped to thecentrifuges is taken, preferably, from near the bottom of tank I), andtherefore the frac tion that is centrifugally purified is the mostheavily contaminated fraction. The mixed oil in tank 0, which has asufficiently high, although not a maximum, degree of purity, is umped,through, a pipe 2', to a tank 7:, which should be provided with knownmeans to prevent overflow. From tank 7: the oil is continuously fed tothe machines.

, direct to aceaaea It is preferred to install two pumps 0, e,

in pipe line d, and two pumps j, y, in p1pe line a. One pump of eachpair may be used at a time; the other being a spare pump for use whilethe first pump is being cleaned.

It is preferred to use at least two centrifugal purifiers g, g. It ispreferred, also, to use both of these centrifuges concurrently,although, for temporary purposes, one of them will sufice while theother is being cleaned. If desired, the oil from the centrifuges may bepassed, through a ipe m, tank It, or to the plpe i eading thereto.

It is possible, for some purposes, to omit the tank a, and flow the oilfrom the machines direct into tank 7). This is practicable if the oilcontains no large, heavy particles that should not go to the centrifuge.

Having now fully described my invention, what it claim and desire toprotect by Letters Patent is:

1. The process of continuously purifying contaminated oil whichcomprises substantially continuously flowing the contaminated oil into abody of such oil in which body the most readily precipitablecontaminating constituents settle by gravity, substantially continuouslywithdrawing oil from which said heavy-contaminating constituents havebeen so arated from the upper part of said body 0 oil into another bodyof oil, substantially continuously withdrawing oil from the second bodyof oil to a locus of purification at a rate substantially less than therate of inflow to said body, centrifugal ly purifying such withdrawnoil, maintaining a substantially constant volume of oil in said secondbody of oil by separately withdrawing from the upper part of said bodyoil, more completely purified than that received the first body of oilbut less completely purified than that from the locus of centrifugalpurification, at such a rate that. with the oil withdrawn forcentrifugal purification. outflows of oil from said second body or oilare established that balance the infiow thereto, and intermingling theless completely purified oil that is withdrawn from the second body ofoil and the more completely centrifugally purified oil.

2. The process of continuously purifying contaminated oil whichcomprises substantially continuously flowing the contaminated oil into abody of such oil in which body the most readily precipitablecontaminating constituents settle by gravity, substantially continuouslywithdrawing oil from which said heavy contaminating constituents havebeen separated from the upper part of said body of oil into another bodyof oil, substantially continuously withdrawing oil from the second bodyof oil to a locus of purification at a rate substantially less than ofinflow said body, centrifugal- 1y purifying such withdrawn oil,maintaining a substantially constant volume of oil in said second bodyof oil by separately withdrawing from the upper art of said body' oil,more completely puri ed than that received from the first body of oilbutless completely purified than that from the locus of centrifugalpurification, at such a rate that, with the oil withdrawn forcentrifugal l purification, outflows of oil from said second body of oilare established that balonce the inflow thereto, conveying bo th streamsof outflowing oil to a third body of oil and'continuously removing oilfrom the third body of oil. R

In testimony of which invention,'I have hereunto set my hand, at NewYork city, on this 20th day oi January, 1926.

ROBERT G. WALKER.

